Fish & Scavenger FAQs

Stock fish, in a new pond, at the rate of one inch of fish for every five to eight gallons of water. (Fish are measured from the tip of the mouth to the tip of the tail.) This low stocking rate allows growth and reproduction. Stock lightly in a new water garden so the fish waste doesn’t overwhelm the bacteria that removes the waste from the water. A mature pond can support an inch of fish for every two gallons of water.

Heavily stocked fish tend to grow slower in a water garden, but will eventually become large, regardless of the size of the pond. It may take longer for a fish to become large if it is crowded, due to competition for food. Large fish have been observed in small ponds. They may be older than similar size fish in a larger pond.

Goldfish and Koi are compatible in the same water garden. Because koi get so much larger, they are often kept in a separate pond from goldfish, but they do not have to be. Koi are sometimes separated because they can be disruptive to plant life by digging up plants and eating their leaves and roots.

Goldfish that are fed regularly will be more active and visible. If they are not fed, they will be very shy, not coming out into open water very often. They can survive with no additional food, subsisting on algae, insects and other organic matter. Feeding with floating pellet foods keeps the fish coming to the surface and learning that when they see people, that it means food. Color enhancing foods can be useful in increasing the color intensity of the fish.

Feed fish only what they can consume in about five minutes per feeding. They can be fed two or three times daily if desired (or not at all if you wish). If uneaten food is left floating on the pond it fouls the water by leaching out nutrients that feed algae. If the fish do not eat the food, net it off immediately. If the fish are fed too much, the water will become fouled either from food that remains uneaten, or from excess fish waste from overeating. Some gardeners increase the use of filtration in order to feed fish more. Use a larger filter, or a more efficient one, along with beneficial bacteria to be able to feed fish more than normal.

In the temperate United States (Zone 5, 6, & 7) goldfish spawn in May and June. Spawning is recognized by vigorous splashing along the edge of the water and relentless chasing of the female fish by the males. The eggs are deposited on underwater plant surfaces, then fertilized by the males. They will hatch in a couple of weeks but the adult fish often eats the young fish (or fry). If you want to keep the fish that spawn, be careful to protect the eggs when you see them. They look like pin head size clear beads that are stuck to underwater surfaces. Usually underwater plants and roots of floating tropical plants (like water hyacinth and lettuce) provide sufficient cover for many of the babies to find shelter. If all fry lived through the earliest stage of growth, you would soon be overpopulated with goldfish. Natural selection reduces the less vigorous young.

You can tell the sex of goldfish during the spawning season by looking closely at the fish while they are swimming around, however, this is easier said than done when the fish are in constant motion. The fish should be four or five inches in length before you can identify males and females. During May and June the adult female fish will usually have a wider than normal body shape. They get significantly larger because they are filled with eggs. The male will remain much sleeker and will display what appears to be salt grains on the gill covers. The male will chase the female, so that means the lead fish is the female and the ones chasing her are the males. There are many more males than female in the average pond, but with the hundreds of eggs laid during spawning, some fish should survive to become adults.

Comet goldfish, the most common variety, will reach 8-15″ at maturity. These fish will reach nearly their full size, then begin growing more slowly. Their bodies grow less, while their fins continue to grow, becoming more flowing. They can live twenty years or more. Shubunkin goldfish grow similarly to comet goldfish. Fantail varieties of goldfish grow to a length of 8-10″ and usually live eight to ten years.

Golden Orfe grow to lengths of fifteen inches or larger very rapidly. It is not unusual for a Golden Orfe to grow from three inches to ten in a single season. They grow more rapidly the first year or two than later years. This variety of fish will live for ten years or more.

Koi, Domestic or Butterfly, will grow to a length of 18-36″ long. They grow rapidly when adequately fed and where they have plenty of room to grow. A well cared for fish can live well over a hundred years.

Fish are not fed at all when the water temperatures drop below 45 degrees. They cannot digest well when temperatures are low. The food will foul the water because the fish will ignore it. When the water is between 45 and 55 degrees, they will eat and can digest foods made primarily with wheat germ. Use only wheat germ foods during cold weather or discontinue feeding altogether.

Fish gasping at the surface indicates a low oxygen level in the water. This is caused by rapid decomposition of organic matter in the water. When a treatment is applied to the water, the oxygen levels drop temporarily because organic matter dies as a result of the treatment. All water treatments must be applied early in the day so the water can recover from oxygen depletion. Treatments late in the day or evening remove oxygen that can not be replaced by normal plant respiration.

Gasping fish need the water to be agitated or oxygenated quickly. A pump gurgling to the surface makes a very efficient oxygenation system. A pump connected to a fountainhead breaks the water into tiny droplets that put oxygen back into the water as well. For a quick temporary fix is to set up an aquarium air pump and air stone to put air bubbles into the water.

Fertilizer for aquatic plants is formulated to be safe for fish and other creatures of the water garden. The tablets are inserted into the soil, then covered, so nutrients are not released into the water. Even if nutrients are put into the water, they make algae grow with no other ill effects.

With the female fish in the lead, the males are chasing her in the annual spring ritual of spawning. The relentless chase may last three or more weeks until spawning has taken place. The males are waiting for the female to lay her eggs on an underwater plant so they can fertilize them.

During the spawning season, it may seem as if some fish are attacking one or more fish in the pond. The males will chase the females around the water garden even into the shallow parts pond’s edge. They may end up on top of potted bog plants or even occasionally splashing all the way out of the pond. There is no harm to the fish unless the female is weakened for some reason and the spawning ritual could cause death. While this is rare, it has been observed.

Koi eat plants including water lilies and bog plants. They eat any vegetation that is in the water. While a koi is small (up to 6 or 7 inches), they do not cause much trouble for plant life. Once they begin to get larger, they can be devastating, devouring plants and muddying the water by constantly rooting around the pots of soil. Use a submerged plant protector or screening to provide a barrier between fish and plants. It is often advised to provide a separate pond for koi, keeping them totally apart from the plants.

Koi can easily attain a length of 24-36 inches if enough room is provided along with ample food. The large koi will also increase in girth as their body lengthens.

Open sores or large pimple-like lesions on the side of a fish are often a result of Ulcer Disease. This contagious and often fatal disease is difficult to control and needs aggressive treatment. Fish that are under environmental stress or are living in poor quality water have a good chance of contracting the disease. Correcting the water quality issues and treating with a product such as Melafix will likely take care of the problem.

A cold water parasite called White Spot or ICH is responsible for what appear to be salt grains on the body and fins of a fish. An advanced case where the body is largely covered is often fatal. Early detection and treatment is imperative. The fish will hang near the surface of the water and act disinterested in food and other fish. This parasite lives in the silt and debris layer of the bottom of the pond and even on the body of a healthy fish. When stresses occur, like a sudden drop in temperature, the parasite becomes free swimming and will attach itself to the fish. Treatment with an ICH control medication that contains formaldehyde and malachite green is needed to eradicate the parasite.

A fuzzy film on the fish is an indication of an injury, parasite or a water quality concern. A fungus that grows on dead or damaged flesh will appear cottony, almost like bread mold. Get rid of the parasites, take care of water quality and provide a topical healing so the flesh repairs itself. Apply a fungal control medication to eliminate the fungus organism and the problem should disappear soon.

Slow moving fish that hang (actually drooping) near the surface of the water indicate a potential illness or water quality concern. Look for spots, redness, torn and frayed fins or any symptom that would indicate a health problem. Check the water quality for excess ammonia, nitrites and high pH and take care of what needs to be fixed. Once the water quality is re-established, the fish should be more vigorous and active.

Goldfish can be grown from eggs providing they are protected from the adults. In a water garden, the fish spawn on submerged plants where the eggs are deposited, then fertilized. Once they are fertilized, the eggs hatch in a couple of weeks. After hatching, the adult fish eat them if they emerge from hiding in the underwater plants. The plants offer protection for a few fish, but often there will be plenty that survive. If all survive, the pond would soon be overloaded with fish.

Spawning mats are sheets of latex coated fibers that provide the fish with a spawning media on which to deposit their eggs. The mat must be moved to another pond where there are no adult fish so the eggs can hatch without the fry being consumed.

One of the best methods is to install a Fish-Spawning Incubator Basket that provides a spawning medium and then a nursery for the young fish. This floating basket is fuzzy on the outside, giving the necessary surface for promoting the release of eggs by the female fish (OK, it tickles her…). Once the eggs are attached to the fuzzy surface, the basket is turned inside out so the fuzzy side is on the inside. The eggs hatch inside the protection of the basket where the adult fish can not get to them. The fry can live in the flow through environment until they are released into the main pond later in the summer.

Goldfish, koi and golden orfe prefer a range of 6.5 to 7.5 for ideal water conditions. This measure of alkalinity or acidity is important because the proper pH determines how well the beneficial bacteria contribute to breakdown of organic waste in the water garden. Too high or too low pH values slow the rate of bacterial activity that can also cause a build up of ammonia, nitrates, and even green water.

Mosquitoes in standing water are best controlled by the presence of goldfish or other fish. The fish consume the larvae of mosquitoes that live in slow moving or still water. Where there are fish, there will be no mosquitoes.

In places where fish can not help, it is possible to control breeding of mosquitoes through the use of bacteria that destroys the larvae. The product is called a Mosquito Dunk®. This product is a floating donut of bacteria laced granules that inoculates the water with the proper dose of bacteria necessary to give 30 days of mosquito control.

All ornamental goldfish varieties, koi, and golden orfe are compatible with each other in a water garden. Use caution when placing koi in a water garden because they will disrupt the plants with their constant digging into the soil where plants are planted.

Snails are in the water garden to consume decomposing organic matter, such as fish waste, algae, excess fish food or wind-blown debris like pollen and dust. They eat this organic waste and further break it down into a finer material that is broken down by beneficial bacteria.

Snails missing from a water garden can often be attributed to a raccoon that is eating them. The snails are often removed completely from the pond for consumption. In getting the snails, the animal often turns over plants or pumps and generally makes a muddy mess. The raccoon usually visits the pond in the nighttime. Live trapping the animal and relocation is the best method of control.

A heron can eat all of the smaller fish, up to six or eight inches in length. Larger fish may simply be speared and tossed out of the pond by the fish to make it easier to catch the smaller ones. The most effective method of deterrence is to string clear fishing line across the pond approximately four to six inches above the water. The strings stretch from one side to the other, crisscrossing back and forth from one end to the other. This hard to see string confuses the bird, making fishing difficult. Tripping up the bird, the string causes the heron to seek easier hunting areas.

Snails are stocked at the rate of one snail for every one to two square feet of pond surface area. Another way to estimate the number of snails is to put them in at the rate of one per every ten gallons of water. This rate allows for growth and reproduction to take place.

Snails are not needed in a koi pond since they are often eaten by the larger fish. If the pond were set-up with a plant pond as the filter for the fish, snails would be included with the plants.

Comet goldfish are the best fish to put into a water garden; they tolerate the most varied conditions present in a pond. They are able to withstand more variation in water quality and temperature than other fish. The second most durable fish are the Shubunkin goldfish. The least tolerant are the fantail varieties.

Natural sea salt is used in the water garden to improve the function of gills and to reduce stress by restoring the slime coating (electrolytes) of the fish. The improved gill function is important during periods of fish illness when the gills are often impaired. Quick salt baths can be helpful in treating external parasites and fungal infections.

Test the water with a Salt Level Test Kit to determine the accurate measure of the salt in the water. For ponds with plants, maintain a salt level of 0.1% or 1ppm. Ponds with fish only can be maintained at 0.3% or 3ppm. The high level of salt is deadly to plant life. Salt does not evaporate, so it is not replaced when fresh water is added.

Ammonia is a toxic substance that is a result of the decomposition of organic fish waste or even decomposing flesh. It occurs during the nitrogen cycle that is a natural process the water garden goes through to rid itself of pollutants. Ammonia eventually breaks down into nitrates that are harmless, the final stage of decomposition of waste. The pond that has an overabundance of ammonia will soon turn green and the fish will exhibit stress. The stress manifests itself in burned gill linings that appear red or inflamed. This eventually results in death of the fish. Once ammonia levels begin to climb, the problem compounds itself by killing a fish that will raise the levels even further. Monitor the ammonia levels, especially in new ponds that do not have beneficial bacteria populations fully established.

Nitrate is the end product of the decomposition of ammonia and nitrite, two harmful by-products of fish waste. Nitrate is harmless to the water garden, contributing only to temporarily green water and acting as a fertilizer to any plant in the water.

Nitrites are a by-product of organic waste decomposing in the water garden. Along with ammonia, these two substances are particularly dangerous to the health of the fish. Beneficial bacteria break down this chemical compound into less harmful nitrate.

During handling of fish, the slime layer that provides protection from infection is reduced and must be replenished artificially. This is often accomplished by applying a stress coat product that instantly restores the necessary protective layer. This is an extremely important step towards fish health. Stress coating products must be applied each time new fish are added to a water garden. Some dechlorinator products have stress coating materials added to them, check the label carefully to be sure.

Chlorine or chloramines are added to kill organisms in the water. This also includes fish and even beneficial bacteria. Remove chlorine by applying a dechlorinator product to the water to remove the deadly chemicals. Do this each time a significant amount of water is added.

Fish generally prefer fish food that is made into sticks or pellets. A commercially made fish food is preferred to things like breadcrumbs or other homemade food. Fish food has balanced nutrition and often includes color enhancers as well. Just like other pets, fish like one food over another and may “turn up their noses” at a new food. Flake foods are not as easily digested and have been associated with digestive problems in outdoor pond fish.

Fish foods that contain wheat germ are more easily digested in cooler times of the season, like spring and fall. This type of food allows feeding in colder water between 45 and 55 degrees. These foods have less protein when the fish require less, thus reducing waste and pollutants in the water.

Fish will be fine without food for a couple of weeks. There is enough natural food that they get to keep them healthy. Algae and zooplankton is sufficient for an indefinite period of time. Reports are often heard of someone getting a neighbor to feed when vacation time arrives. The good intentioned neighbor might overfeed the fish and all the fish may die while the vacationer is gone.

The best way to feed during vacation is to install a feeder block. This is a calcium block that is impregnated with food pellets that provides continuous feeding. A floating ball appears when the food is used up, signaling time for replacement. This safe method is foolproof even for the neighbor to employ.

Goldfish are not plagued with too many ailments in a healthy water garden. Poor water quality causes fish problems like fungal infections. A cottony material on the fins or body is often a result of an insufficient ecological balance in the water garden. New ponds, overstocked ponds or dirty water gardens can be more susceptible to fungal infections.

Parasites can be transferred from one fish to another so it is imperative to know of a reliable source of fish when adding new fish to an existing population. Water should be fully dosed with a stress coat product each time fish are handled or added to.

Cold water parasites like White Spot (Ich) are prevalent in spring and fall or can become apparent after a sudden severe downpour that drops the water temperature. Apparently healthy fish become infested by the organism that resides in the debris layer at the bottom of the pond. Medicated treatment is simple and effective if done early enough.

General lethargy of the fish, lack of appetite or staying separate from other fish is a sign of many ailments, sort of an early warning. Inspect the fish carefully for symptoms that may be signs of various ailments. Any advanced physical symptoms, especially open sores or torn fins must be taken care of quickly.